Grill system and method for detecting movement when motor is &#34;off&#34;

ABSTRACT

A grill including a first platen assembly, an second platen assembly movable with respect to the first platen assembly, a motor operable to move the second platen assembly with respect to the first platen assembly, and a control operable to measure movement of the second platen assembly with respect to the first platen assembly while the motor is off.

BACKGROUND

The present disclosure relates to a grill and, more particularly, tosystem for detecting a position thereof.

Grills or griddles are used to cook various foods, such as hamburgersfor example. A conventional clamshell grill generally includes a secondplaten assembly movably connected to a first platen assembly. Forexample, the second platen assembly may be pivotally coupled to thefirst platen assembly for movement between a lower cooking positionoverlying the first platen assembly and a raised position inclinedupwardly from the first platen assembly. When the second platen assemblyis in the lowered cooking position, a gap is created between the upperand lower platen assemblies. This gap is generally adjustable accordingto the thickness of the food being cooked. For example, hamburgerpatties are preformed in several different sizes (i.e. a quarter poundpatty has a greater thickness than a regular patty). To cook the food,an operator selects the gap size and a cooking time via an operatorinterface for the food item being cooked.

A sensor may be utilized to identify when the upper platen is closed soa solenoid latch may be engaged. This is past a resting “closed”position so the latch doesn't inhibit closing of the platen. After thesolenoid latch is energized, the motor is turned “off” to allow theupper platen to rise against the latch under a spring bias. The sensorusually shows an open state at this point as if the hall effect sensorwas adjusted to show a “closed” state when the solenoid is engaged, itwould engage too soon and the latch would prevent full closing of theupper platen.

SUMMARY

A grill according to one disclosed non-limiting embodiment of thepresent disclosure can include a first platen assembly; a second platenassembly movable with respect to the first platen assembly; a motoroperable to move the second platen assembly with respect to the firstplaten assembly; and a control operable to measure movement of thesecond platen assembly with respect to the first platen assembly whilethe motor is off.

A further embodiment of the present disclosure may include a latchmechanism configured to selectively couple the second platen assemblywith respect to the first platen assembly.

A further embodiment of the present disclosure may include a springmechanism operable to bias the second platen assembly toward the openposition.

A further embodiment of the present disclosure may include, wherein thecontrol is operable to intermittently short a motor coil of the motor sothat back EMF causes current to flow in the motor coil in response tomechanical movement of the upper platen assembly.

A further embodiment of the present disclosure may include measuring thecurrent to identify a relatively position of the upper platen assembly.

A further embodiment of the present disclosure may include measuring thecurrent to identify a latch failure.

A further embodiment of the present disclosure may include measuring thecurrent to identify an over travel adjustment.

A further embodiment of the present disclosure may include measuring thecurrent to measure a position of the upper platen assembly.

A method of detecting movement of a grill platen while a motor is off,the method according to one disclosed non-limiting embodiment of thepresent disclosure can include shorting a motor coil of a motor operableto move an second platen assembly with respect to a first platenassembly so that back EMF causes current to flow in the motor coil inresponse to mechanical movement of the upper platen assembly; andmeasuring the current to identify a relatively position of the upperplaten assembly.

A further embodiment of the present disclosure may include, whereinidentifying a relatively position of the second platen assembly includesidentifying a latch failure.

A further embodiment of the present disclosure may include, whereinidentifying a relatively position of the second platen assembly includesidentifying an over travel adjustment.

A further embodiment of the present disclosure may include whereinidentifying a relatively position of the second platen assembly includesmeasuring movement of the upper platen assembly.

A further embodiment of the present disclosure may include, whereinidentifying a relatively position of the second platen assembly occurswhile a spring mechanism is biasing the upper platen assembly.

A further embodiment of the present disclosure may include whereinidentifying a relatively position of the second platen assembly occurswhenever the second platen assembly is not moving.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be appreciated; however, the following descriptionand drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiment. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is a perspective view of an example grill system according to onedisclosed non-limiting embodiment;

FIG. 2 is a schematic view of a motor for the grill system;

FIG. 3 is a schematic view of a motor for the grill system;

FIGS. 4 and 5 are phase diagrams of the motor.

FIGS. 6, 6A, 6B are block diagrams of a method of detecting movement ofa grill platen while a motor is off according to another disclosednon-limiting embodiment.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a grill system 20. The grill 20includes a rigid base structure 22 to support a first platen assembly 24and a second platen assembly 26. The second platen assembly 26 may bemovably attached to the base structure 22 with a mounting structure 28such that the second platen assembly 26 is configured to move between alowered, cooking position and an upper raised position relative to thefirst platen assembly 24. It should be appreciated that although aparticular relationship of the upper and lower platen assembly aredisclosed, either the first and/or second platen assembly may bemovable.

In one embodiment, the mounting structure 28 is a hinge 43 such that thesecond platen assembly 26 is configured to pivot relative to the firstplaten assembly 24; however, in other embodiments, the second platenassembly 26 may be lowered and raised in a generally linear motion. Thesecond platen assembly 26 may be moved between the raised and loweredpositions either automatically or manually. In embodiments where thesecond platen assembly 26 is moved manually, the second platen assembly26 may include a handle 30 that can be grabbed by an operator to movethe second platen assembly 26 between the raised and lowered positions.

The first platen assembly 24 includes a lower grilling plate 32 and thesecond platen assembly 26 includes an upper grilling plate 34. Fooditems are placed on the lower grilling plate 32 by the operator forcooking. A motor 35 (illustrated schematically) is operable to move thesecond platen assembly 26 between the opened and the lowered positionsuch that the one or more food items to be cooked are positioned withina gap 36 formed between the upper and lower grilling plates 32, 34, thenlatched with a latch 37 such as via the handle 30.

The grilling plates 32, 34 are heated by a heater (not shown) to cookthe food items. In order to transmit heat to the food item the grillingplates 32, 34, respectively, may be formed of a heat-conductingmaterial, such as cast aluminum, abrasion resistant steel, cast iron,stainless steel, mild steel, a ceramic material, or other suitable heatconducting materials used in grills. Although the grilling plates 32, 34are shown as having a rectangular shape, one or both of the grillingplates 32, 34 may also be formed into other shapes, such as circular oroval shapes tor example. Although a single grill is described in detail,a plurality of individual grills 20 may be arranged adjacent one anotherto form a grill assembly.

With reference to FIG. 2, the motor 35 is operable in response to acontrol system 50 to move the second platen assembly 26. The motormovement for a close cycle may include an acceleration phase, a steadyrun rate phase, and a deceleration phase. In one embodiment, the motor35 turns a lead screw in a linear actuator 41 such that there is 0.500inches travel per shaft revolution with about 5 inches total travel toraise or lower the second platen assembly 26.

While closing the second platen assembly 26, deceleration must begin ata particular point in the close cycle to bring the second platenassembly 26 to a smooth stop. If the operator has manually moved theplaten prior to motor driven closing, the control system needs to trackthis movement so the point to begin deceleration point can berecalculated. Subsequent to closing the platen, a latch solenoid 40 isactuated to latch the second platen assembly 26 to the first platenassembly 24. In one embodiment, the latch solenoid 40 is stationary onthe bottom and the latch 37 slides over it. When the solenoid 40 isenergized, the two balls on the side of the solenoid 40 protrude toengage the latch 37.

The motor 35 is then deactivated to allow a spring mechanism 42 toslightly open the second platen assembly 26 and be retained against thelatch 37. That is, once the motor 35 is deactivated the spring mechanism42 operates to push the second platen assembly 26 toward the openposition until retained by the latch 37. If the latch solenoid 40 failsto engage the latch 37, the spring mechanism 42 will raise the secondplaten assembly 26 to full open position. Tracking motor movement whileoff allows detection of latch failure. These and other situations makeit desirable to detect movement of the platen while the motor isdeactivated.

The control system 50 can include a control module 60 with a processor62, a memory 64, and an interface 66. The processor 62 can include anytype of microprocessor or other processing device having desiredperformance characteristics. The memory 64 may include any type ofcomputer readable medium that stores the data and control processesdisclosed herein. That is, the memory 64 is an example computer storagemedia that can have embodied thereon computer-useable instructions suchas a process that, when executed, can perform a desired method. Theinterface 66 of the control module 60 can facilitate communicationbetween the control module 60 and other systems.

With reference to FIG. 3, according to one embodiment, the motor 35 maybe a 2 phase bi-polar stepper motor design. Each coil is driven througha full-bridge (Q1-Q4) and (Q5-Q8) to allow the polarity of appliedvoltage to be varied. Transistors Q1 and Q4 are turned on while Q2 andQ3 are off to apply positive voltage to motor coil A. Transistors Q2 andQ3 are turned on while Q1 and Q4 are off to apply negative voltage tocoil A. Q5-Q8 perform similar role for coil B. While each coil isactively driven, coil current flows through shunt resistors R1 or R2.The voltage across these shunt resistors is proportional to the currentin the motor coil. The coils are pulse-width modulation (PWM) dutycycled and the current in each coil is measured each PWM cycle. The PWMduty cycle is adjusted, cycle by cycle, to maintain the desired currentlevel. In this example, the motor has 200 steps per revolution. Eachfull step may be split into ¼ a sine period to allow the drive to be“microstepped” to produce smoother movement. (FIGS. 4 and 5).

The motor 35 generates voltage when the motor shaft 39 rotates. The EMFgenerated by the motor provides a mechanism to detect and track manualmovement of the upper platen while the motor is “off”. The hardware neednot sense this voltage directly as the coils may be momentarily shortedso the generated voltage causes current to flow in the motor coils. Thecontrol measures the resulting current to detect motor movement. Themotor coils can be shorted by turning on transistors Q2 and Q4 for Coil“A”, and transistors Q6 and Q8 for coil “B”.

This current operates to resist mechanical movement. This providessignificant resistance to moving the shaft 39 such that the faster themovement, the larger the dampening force. The length of time the coilsare shorted may be varied so that current flowing in the coils isreduced and mechanical loading is negligible. This allows movement to bemeasured over a relatively large speed range.

To further avoid such significant resistance to movement, only one coilis shorted at a time, and for only long enough to develop measureablecurrent from the EMF. The amount of time the coil is shorted iscontrolled in time proportionally to the detected speed of the motor.Coil current flows in the shunt resistors (R1 and R2) only while thecoils are being actively driven. Since driving the coil causes currentto flow in the coil, the drive pulse to measure current is only 1.5 uSwide so that coil inductance prevents significant current flow duringmeasurement. The drive polarities can also be alternated so this slightbias current does not bias the overall movement detection.

The sensed current produces a signed value that provides magnitude aswell as polarity. When magnitude is above a threshold, the motor coilquadrant is known. By comparing changes in quadrants of the two coils,the speed and distance of motion can be determined. The speed is nototherwise required other than to adjust the time to short the coils.Counting movement may be performed to determine shaft position.

With reference to FIG. 6, in one embodiment, a method 100 of detectingmovement of a grill platen while the motor is off is schematicallyillustrated. Initially, the method is initiated by processing thecurrent samples to determine coil polarity and if motion has occurred(step 102; FIG. 6A), then the bridge state for the next period is (step104; FIG. 6B).

More specifically, the current sample for each coil is processedseparately. Processing is initiated by determining the current state,e.g., was current sensed last period (step 110); is the current samplegreater than the previous peak (step 112); is current polarity differentthan previous state (step 114) and is current sample greater thanthreshold (step 116).

Next, once movement has been detected, the polarity state for this coilis set (step 120). Next, the movement direction is determined based onpolarity of both coils (step 122). Time is then set since last movement(step 124). Finally, the timer is restarted for the next detectedmovement (step 126).

Next, the bridge states are set for the next period (step 130) viamovement detection timer being greater than the last movement time (step132). If movement has not been detected by the time last movement wasdetected then the time is extended to short the coil for longer periodto increase sensitivity.

The last movement time is set equal to movement detect timer (step 134).Finally, time to short the coils is calculated and off time is based onlast movement time (step 136).

This method facilitates smoother closing of the second platen assemblyif the operator manually moves the platen, detection of a failed latchsolenoid, and automated measurement of the over travel adjustmentbetween latch switch and latch solenoid without changes to hardware oradditional product cost.

The elements disclosed and depicted herein, including in flow charts andblock diagrams throughout the figures, imply logical boundaries betweenthe elements. However, according to software or hardware engineeringpractices, the depicted elements and the functions thereof may beimplemented on machines through computer executable media having aprocessor capable of executing program instructions stored thereon as amonolithic software structure, as standalone software modules, or asmodules that employ external routines, code, services, and so forth, orany combination of these, and all such implementations may be within thescope of the present disclosure.

It should be appreciated that relative positional terms such as“forward,” “aft,” “upper,” “lower,” “above,” “below,” “bottom”, “top”,and the like are with reference to the normal operational attitude andshould not be considered otherwise limiting.

It should be appreciated that like reference numerals identifycorresponding or similar elements throughout the several drawings. Itshould also be appreciated that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom.

Although the different non-limiting embodiments have specificillustrated components, the embodiments of this invention are notlimited to those particular combinations. It is possible to use some ofthe components or features from any of the non-limiting embodiments incombination with features or components from any of the othernon-limiting embodiments.

Although particular step sequences are shown, disclosed, and claimed, itshould be appreciated that steps may be performed in any order,separated or combined unless otherwise indicated and will still benefitfrom the present disclosure.

The foregoing description is exemplary rather than defined by thelimitations within. Various non-limiting embodiments are disclosedherein, however, one of ordinary skill in the art would recognize thatvarious modifications and variations in light of the above teachingswill fall within the scope of the appended claims. It is therefore to beappreciated that within the scope of the appended claims, the disclosuremay be practiced other than as specifically disclosed. For that reasonthe appended claims should be studied to determine true scope andcontent.

1.-8. (canceled)
 9. A method of detecting movement of a grill platenwhile a motor is off, the method comprising: shorting a motor coil of amotor operable to move a second platen assembly with respect to a firstplaten assembly so that back EMF causes current to flow in the motorcoil in response to mechanical movement of the upper platen assembly;and measuring the current to identify a relatively position of the upperplaten assembly.
 10. The method as recited in claim 9, whereinidentifying a relatively position of the second platen assembly includesidentifying a latch failure.
 11. The method as recited in claim 9,wherein identifying a relatively position of the second platen assemblyincludes identifying an over travel adjustment.
 12. The method asrecited in claim 9, wherein identifying a relatively position of thesecond platen assembly includes measuring movement of the upper platenassembly.
 13. The method as recited in claim 9, wherein identifying arelatively position of the second platen assembly occurs while a springmechanism is biasing the upper platen assembly.
 14. The method asrecited in claim 9, wherein identifying a relatively position of thesecond platen assembly occurs whenever the second platen assembly is notmoving.